Altimeter



F. COREY ALTIMETER Oct. 24, 1933.

Filed May 6, 195@ 2 Sheets-Sheet l INVENTOR ffy C011?. y

.,M .2 f n 0 a L a l W y 4 a M am Y ATTNY Oct. 24, 1933. F CORE-Y l 1,932,066

ALTIMETER I Filed May 6, 1930 2 Sheets-Sheet 2 g" 4 rwa-:s

Patented Oct. 24, 1933 `I UNITED STATES PATENT oT-FICE 1,932,066 ALTIME'rEn Flournoy Corey, Detroit, Mich., ...assigner to Westinghouse Electric & .Manufacturing Conipany,- a corporation of.Pennsylvania Application May 6, 1930. Serial No. 450,107

8 Claims.

My invention relates to means for correcting the indications of-one variable factor in accordance with changes in another to obtain a cor-- rected value and it has particular application .to

`5 a device for use with altirneters, such as that described in the copend'mg application of Lewis W. Chubb, Serial No. 446,634 filed April 23, 1930 and assigned to the Westinghouse Electric '& Manufacturing Company.

. The device described in the Chubb application is a wave impulse-emitting device or transmitter disposed on the-aircraft and .which projects wave impulses, such as sound or radio waves, toward the earth below the aircraft. The wave impulses are then reflected to the aircraft, and their angle,

with'respect to a reference plane at the aircraft,

is measured. The velocity of the aircraft is meas- 'uxed in any well known manner. Knowing the velocity of the aircraft in a horizontal direction and the angle, termed the angle of depression, at which the reflected waves are received, the height .of the aircraft may be determined with raccuracy.

' In order to better understand the operationof the device, it is desirable to, develop the trigonometric equation utilized in nding the height when the velocity and the angle of depression :are known.

Referring more particularly to Fig. 1 of .the drawings, let

L=the length of the .fuselage of the plane between the. transmitter and the receivers t=the time from the emissiony of a wave impulse from the transmitter Auntil the reflected impulse lis received at the receiver a=the velocity of sound` v=the velocity ofthe aircraft y h=the height to be measured y=distance traveled by wave' impulse from transmitter to the earth or from earth' to vthe v '40 receiver.

'=the angle' of depression, and

2D=length of airplane+distance travelled lglhile sound goes to earth and returns to'receiv'er again,`

:Simplifying 610) we'obtaim- It 'therefcrefbe :understood that, :knowing the velocity oi 'the aircraft .land *the Vangle of :de-

pression the Aaltitude -oi 'the aircraft Jcan .readily be ascertained.

AIt `will be Aseenztliat .thechubbaequation .is tbased .on .the velocity vol! fthe .aircraft with vrespect to-fthe ground or fgroundfspeed. lSince it is diillcult v'to :obtain .a-.direct 'reading .meter for ground speed,

I prefer kto utilize an air-speed :meter :to measure the velocityiactor .of the Chubb equation. This gives `rise to slight inaccuracies lwhich :do not ybe Alili device which permits the combination of an altimeter with an air-speed meter.

Still other objects of my invention will become apparent from the following description, taken in conjunction with the drawings.

Referring to the drawings, in which like figures indicate like parts: j

Figure 1 is a diagram illustrating how wave impulses sent from the aircraft and reflected from the ground are received at different angles, with reference to a horizontal plane, in Vaccordance with changes in altitude.

Fig. 2 is a side elevational view of an airplane having an altitude-indicating device incorporated in the structure.

Fig. 3 is an enlarged plan view of the dial shown in Fig. 4.

Fig. 4 is a diagrammatic View of the control system utilized in 'ascertaining the angle at which the reflected sounds are received, and also of the device utilized in combining the readings of the angle-measuring device and an air-speed meter.

Fig. 5 is a diagram of the control circuit em' ployed, and l Fig. 6 is a graph showing the relation between indicated altitudey readings at two different air speeds.

While my device is particularly useful in conjunction with a depth-sounding device or an altimeter, such as isshown in the Chubb application, it is apparent that lthe device may be readily utilized whenever it'is necessary to correct one set of indications in accordance with another set of factors.' 1

In the Chubb invention, a wave-impulse-emitting device or transmitter is provided on the aircraft to project the wave impulses, such as sound.

or radio waves, toward the earth below the air` craft. These waves are sent out in all directions but, of course, only one given set of reflected impulses are received at the aircraft. Owing to the movement of the aircraft through the air and the distancefrom the transmitter to the receiving elements, the waves, reflected from the earth below, are received at an angle, with regard Ito a horizontal plane, which varies in accordance with variations in the altitude of the aircraft. The velocity of the aircraft is preferably measured by an air-speed indicator which gives rise to certain inaccuracies since the Chubb equation is based on ground speed, but the inaccuracies are negligible. Knowing the air speed of the aircraft, and

' the angle, termed the angleof depression, at'

of the fuselage where it is out of the way and is less subject to the influence of the motor and the propeller. The wave-impulse-receiving device, such as the microphones shown, are preferably mounted below the wing, for a reason to be hereinafter explained.

With particular reference to Fig. 2 of the drawings, two arms 10 and 11 are provided, one above and one below a horizontally extending air foil, such as the wing 12 of the airplane. Levers 13 and 14 are pivotally mounted on the ends of the arms in such manner that the levers may be oscillated in a vertical plane parallel to the direction of fiightof the aircraft. The levers are pivotally mounted at their centers and carry microphones 15, 16,17 and 18, at their ends. The control system for moving the levers and the microphones is shown schematically in Fig. 4. It is to be noted that the levers are to be moved simultaneously in opposedrelation to each other so that, for instance, while the lower lever 14 is at a given positive angle with reference to a plane equally distant from the ends of the arms, the upper lever 13 is yat an equal negative angle with reference to the plane. Control of the levers and the positionof the` microphone is secured by means of a combined control and indicating device, such as the pulley 21 shown in Fig. 4. The controls, as exemplified by the cords 22 and 23, are adapted to be moved simultaneously in opposite directions by the pulley 21 to which .the cords are fastened. The pulley is provided with an axially extending scale 24, as shown -in Figs. 3 and 4, which has vertically extending divisions '25 for indicating air speed and horizontallyl extending divisions 26 for indicating altitudes.

An air-speed meter of the usual type, as, for instance, a Venturi meter or a wind plate 27, is mounted,l on the airplane at a position such that it is moved against the force of the calibrated lthe vertical lines 25, the air speed of the aircraft,

and, when the microphones have been properly adjusted, to indicate the angle of depression, the pulley scale 24 has been moved underneath the hair'lines of the pressure-indicating device to indicate the altitude of the aircraft, with values for the air speed of the aircraft superimposed upon the value of the angle of depression.

It is to be understood that the control device has been shown diagrammatipally only and any suit able mechanism may be employed without departing from the spirit and scope of the invention. as expressed in the claims. v

Referring more particularly to Fig. 5, the two microphones'l'l and 18, disposed below the wings, are connected in parallel electrical relation to the power supply 31 and each microphone is connected in series electrical relation to portions 32 and 33 of the opposed windings of the receivers Rr.. and Ra, respectively. The two microphones 15 and 16, disposed above the wing, are connected in parallel electrical relation to each other and to the two lower microphones across the terminals of the power supply 31,` but each of the upper microphones is connected in series electrical relation to other portions 34 and 35 of the receiver windings Rn and Rr., respectively. Thereceivers s RL and Ra are the usual receivers employed in binaural searching circuits, 'and one receiver Ra 150 ference in height readings and. 84 miles.per hour.

1,932,066 isv appliedtothe `right ear andthe'kothcr Rr. tol

the left ear.j y

In determining the altitude:v of the aircraft. the operator adjuststhe position of the microphones 17 andk 18, `by. 'means of the pu1ley`21,

until the sound of theadvancing reflected wave fronts .seems to bein the middle of his head@ This means that the microphones l'land 18 arebe'ing simultaneously .affected 'by v.the ladvancingfwave fronts and are, therefore, parallelfto them.. The f pointer 28 ofl the air-speed meter'fZ'l movesacross ordinates. Fig. c iiiustratesgrapnicily the difson of the angle made bythe leverk arm 14 with respect to a giyeneference plane, such as thewith ,reference tothe air speed pf the aircraft.`

- The microphones 1'5' and 16, ofcourse, move in synchronism withfthe microphones l'land 18 eX- ,'of.reflection` of @the vsound wave v said adjusting cept that their movement is 'inthe opposite direchorizontal plane of the aircraft and 'correctedl tion. ,Microphones 15 and 18, forlinstance", willbe located at substantially the .sarne'distancefrom' the transmitter, the motor' and the. propellerjat all times and, therefore'sound coming direct from the transmitter,` the motor and propeller,tv illfen-j.` ergize the windings 33-and 35.91. the reciver RL in opposite directions so that the effect o f sounds travelling in a horizontaljdirection is balanced out by means of the electricalimpulses which act against each other.

The same is true of microphones 16 and 17 withl respect to the receiver windings 34, and 32 of receiver Ra, and a sound wave which strikes microphones 16 and 17 will cause an equal and opposite electrical disturbance in the receiver RR which will balance out.

The horizontally extending wing 12 acts to shield the upper set of microphones and, therefore, the reflected sound from the ground below will aiect only the microphones 17 and 18. The operator, as has been explained, may move the microphones until the sound `in the receivers seems to be in the center of the head, by reason of the well known binaural phenomena, and he can then read from the indicating device, by my invention, the height of the aircraft corrected for air speed.

It is to be noted that the crossed hair lines of the indicating device also may be utilized to ascertain the air speed of the aircraft, since the indicator moves from left to right and right to left directly in accordance with the air speed and the scale below the indicator is divided vertically into units of speed in miles per hour.

In view of the foregoing, it will be apparent that the invention provides for giving the pilot of an aircraft a direct indication of his height above the earth witha reasonable and safe degree of accuracy. The accuracy of the indication is more than sufficient for all practical purposes when all of the factors giving rise to the slight inaccuracy are taken into consideration.

As pointed out hereinbefore, the slight error due to the use of air speed instead of ground speed is negligible because of the smallvariation or change in the altitude readings for different velocities of the aircraft, as shown in Fig. 6. f

The hair lines `29 oftheindicator, therefore,jv show directlythe altitude oftheaircraft by rea- There may` bealso some slight'v inaccuracy 'of the indication' because of the soundly/aves being carried bythewi'nd, but,.s`inc'e"th e wind velocity is usually so low in comparison to the speed at ,which the'sound wavestravelthis cause of inaccuracy become'spurely theoret icalI and of v4.no

changes in air Vjdensity vr'at different altitudes, vthereby causing some "slight variation in pressure ,fonijthe air spe'ed lindicator,y mayv be also eliminated to af substantial degree by utilizing lthe average pressureand designing orcalibrating the indicating devic'efer' .thislprsurellfl i L L It lis apparentr that modifications may, be made bythoseskilled lin the artand such modincatlons may be made without departing from the spirit n'd' `scopeffof my linvention; as set 'forth in the appended Claims.- j

I claimjas my 'lnventiom' 1 1. Injcombinationwitli anv aeroplane, means carried j by' the ''aeroplane'k `for emanating sound .waves to be Areflected fromtlie' earth, `vineafnsjcar- 'riedibyy v.the aeroplaneifor receiyingthe reflected fspund wayesgimeanjsfforgdjustmg the' positip'ncf`I the receiving means in accordancewith Vthe angle and, .means responsive to the Q air speed ofthe' aeroplane'y for correcting the' reading of the indicating' device in IaccoVrdance.fvvitliftheair speedv of 2. The cdmbination' aicrafeniens, 'Ciargrijed'b'y thplgircraft foremimng 'sound waves to 'be reflected from theeath' while .the aircraft isin flightwave receiving means carried by the aircraft for-receivingth reflected waives,- means including a scale fory adjusting lvthe` wave receiving means to measure the angle of reflection off the waves and indicate the angle on the scale, and means including an index pointer responsive to the air speed of the moving Aaircraft for cooperating with the scale whereby the angle of reflection which is proportional to the altitude of the aircraft is corrected for air speed.

3. The combination of an aircraft, means carried by the aircraft for emitting sound waves to be reflected from the earth while the aircraft is in flight, Wave receiving means carried by the aircraft for receiving the reflected waves, means for adjusting the wave receiving means in accordance with the angle of depression of the sound waves, a scale prvided-with an index pointer which is stationary with respect to the direction of movement of the scale and movable in a direction at right angles to the direction of movement of the scale, said scale being actuated in accordance with lthe movement ofthe wave receiving means and disposed tol-indicate the alv titude of the aircraft, and means' responsive to the air speed of the aircraft for actuating the index pointer, thereby toindicate directly the altitude of the aircraft at any particular air speed.

4. In combination with an aircraft, means on the aircraft for transmitting sound waves to be reflected by the earth, means including a pair of sound detectors mounted on a movable sup--` porting member for measuring the angle of de pression of the sound waves, means for adjusting the movable supporting member to an angular position corresponding to the angle of depression, a device responsive to theA air speed of .the aircraft, and an indicating device dis- 'aircraft abovethe earth. Y. 5. In combination with an aircraft,` means on ythe aircraft for transmitting so'undwaves to'fbe reflected by, the earth,y means includingaj pair the adjusting means; sound Vdetectors and their supporting member and the device responsive to the air speed fri'ndicating the jlieightlofv the of sound detectors mounted on ya movable supaircraft, ,and la 'device for indicating the v height ment of tbe sound detectors and their supporting j; or movement cri the scaiepsaidgfpointer beim;V

member and a D0ini1r. disposed to moved acrossthescale atrigh't angles'toth'e direction actuatedby the airspeed ln spon'sive device;

6..In/combination withjan aircraft, :means on the aircraft for"r transmitting sound wave s 't o be porting member for measuring i ;he L angleof desupporting member for the soundsdetectorsfsaid being yia'iovideci with asc/ale havingjrefer-- ence lines" indicating" 'distance above the f earth 'and intersecting; reference lines mamans' Y:mr

speed, -en .niridex p vointex'v associated with the drum element and movable only in a direction'at right anglesto the' d irectionof movement of the drum ythe index'pointer. 1

posed to beLjointly actuated in accordance with 7. In combination with an aircraft, means upon the aircraft for producing sound waves, a plurality of pairs of electricallyconnectedsound detectors mounted on the aircraft, means for [simultaneously rotating the pairs of sound detectors to lmaintain them symmetrically disposed vrelative to the means for producing sound waves,

receiver meansconnected to the sound detectors yinl apredetermined'manner whereby the operator jmay determine the position to which `the sound detectors are to b e rotated, a scale associated with: the means for rotating the sound deteetorsdisposedto indicatheamtude or the aircraft as'determined by 'the anglev of depression foffi the reflected lsound waves, an index pointer associated with the scale vand `disposed 'to be movedjacross thescale at right angles to fits direction of movement; `and 'means movable in proportion toA the air speed vfor adiusting'the position of the index pointer, thereby to Lprovide" a direct indicationv Lof `the altitudeo f the s aircraft in accordance withits air'speed.

'3.` In combination with an aircraft, means upon 'the aircraft -fc" r emitting sound waves, means, includins a movable member, upon the pointer-'in "a' direction at right angles to the direction ofj movement of the scale, 'means movable 'in proportion to, the airspeed of the air- FLoUnNoY' com.'

aircraft tol measure the angle between the sound beam ree'cted fromthe earth and the axis oi' theaircraft; "a scale.A means operatec'iV by the 'movable member-to move the scalel ina predetermine'fi relationf to the motion of the movable jmeluber, index pointer f disposed to cooperater with "the scale,' and means*to' `move 'the index craft, and .means formoving the 'index means by s' V the' air speed means,kr element, and means `responsive"to the airspeed 'oftheaircraft for. controlling the"`inove ment of4 

